The proper function of CNS axons depends on accurate and complete myelination by oligodendrocytes, which are generated by precursor cells (O-2As) during early development. The extent to which the CNS has the ability to generate new oligodendrocytes after injury or demyelinating diseases such as Multiple Sclerosis is unknown. Oligodendrocyte precursor cells persist in the adult CNS in appreciable numbers and thus have been hypothesized to be a likely source of new oligodendrocytes. My experiments are designed to examine the potential of adult O2As to generate oligodendrocytes by first comparing the properties of purified perinatal and adult O2As in vitro using clonal analysis. My preliminary results show that adult O2As so far appear to be qualitatively similar to perinatal O2As but quantitatively different in that they divide much more slowly. I will further find out whether this difference comes from replicative senescence of O2As. Then, I will determine whether adult O- 2As can revert into perinatal O2As. Lastly, I will test whether purified adult O2As will support remyelination when transplanted into mutant rats with demyelinated white matter. The long term goal of this research is to enhance effective remyelination after injury or demyelinating diseases of the CNS.